JPH089483B2 - Method for producing granular insoluble sulfur and rubber composition with improved fluidity - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for producing insoluble sulfur having improved fluidity and a rubber composition, which is capable of improving workability in compounding rubber and rubber properties in vulcanizing the rubber composition. it can.

[0002]

2. Description of the Related Art Insoluble sulfur is usually composed of fine particles of about several tens of microns or less, which scatters as dust during handling and is easily charged with static electricity. There is a problem that the trouble occurs.

In order to solve these problems, a rubber process oil composed of one or a mixture of two or more selected from naphthene-based, aromatic-based and paraffin-based powders is mixed with insoluble sulfur powder, so-called oil. Used as treated insoluble sulfur.

However, although the oil-treated insoluble sulfur has less dust scattering and damage due to static electricity as compared with the untreated one, it lacks fluidity and adheres to various devices and containers during handling. For example, when measuring insoluble sulfur using a measuring instrument and transferring it to the next step, a part of it adheres to the inner wall of the container and reduces the accuracy of measurement, and the rubber composition changes. There were problems such as variations in the physical properties.

As a means for improving the fluidity of insoluble sulfur, there is known a method in which oil-treated insoluble sulfur is subjected to pressure molding to give a granular form. However,
In this case, the insoluble sulfur agglomerates hard, and when kneaded with the rubber, the granular insoluble sulfur remains without collapsing into the original powder state, so that the dispersibility in the rubber decreases and the physical properties of the rubber vary.

Japanese Unexamined Patent Publication (Kokai) No. 62-246810 discloses a method of mixing a dry powder of insoluble sulfur and a rubber processing oil in a predetermined amount to form granules, and further spreading a dry powder of insoluble sulfur on the surface thereof. However, in this manufacturing method, when the mixing ratio of the rubber process oil is small, the powdery insoluble sulfur spread on the surface is scattered, and if the addition amount of the rubber process oil is large, adhesion problems will occur. was there.

[0007]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned problems of fluidity of insoluble sulfur, especially the adhesion to the vessel wall, and to improve the dispersibility in rubber to improve the physical properties of rubber. To obtain a rubber composition with less variation.

[0008]

Means for Solving the Problems The present inventors have conducted various test studies in view of such circumstances, and as a result, granulated an insoluble sulfur powder by mixing an organic solvent or an organic solvent and a rubber process oil. Then, by heating this to a temperature of 120 ° C or lower to volatilize the organic solvent and make insoluble sulfur or a mixture of insoluble sulfur and rubber processing oil into granules, the fluidity and the adhesion to the vessel wall are significantly increased. Can be improved to
Furthermore, since this granule has an appropriate breaking strength, it easily disintegrates when kneading with rubber, and the insoluble sulfur returns to the original powder state, so that the rubber composition has good dispersibility in rubber and little variation in rubber physical properties. The present inventors have completed the present invention by finding that the product can be obtained.

Typical organic solvents used in the production of the granular insoluble sulfur of the present invention are n-hexane, carbon tetrachloride, alcohols such as isopropyl alcohol, toluene and the like. The powder may be mixed at a ratio of 0.3 to 0.7 liter with respect to 1 kg of the powder.

When an organic solvent having a boiling point of more than 120 ° C. is used, the temperature of insoluble sulfur should be kept at 120 ° C. or lower by heating under reduced pressure. If the amount of the organic solvent added is less than 0.3 liter per 1 kg of the insoluble sulfur powder, it becomes difficult to granulate the powdery insoluble sulfur to 0.7.
If it exceeds liter, the product becomes creamy, which is not preferable.

In the practice of the present invention, when an organic solvent and a rubber process oil are added to insoluble sulfur, 0.2 to 0.6 liter of the organic solvent is added to 1 kg of insoluble sulfur.
Rubber process oil should be used at a rate of 0.01-0.30 kg. The rubber process oil suitable for carrying out the present invention is one kind or a mixture of two or more kinds selected from naphthene type, aromatic type and paraffin type.

The rubber composition of the present invention comprises the above-mentioned insoluble sulfur or granules comprising insoluble sulfur and rubber process oil,
0.5 parts by weight of insoluble sulfur or 100 parts by weight of rubber
It should be blended so as to be 10 parts by weight.

If the amount of insoluble sulfur added to the rubber exceeds a predetermined amount, the heat aging property of the rubber deteriorates, and if the amount is less than the predetermined amount, the rubber will not sufficiently crosslink.

[0014]

The insoluble sulfur powder usually contains about 2 to 4% of soluble sulfur, and when an organic solvent is added to this insoluble sulfur, the soluble sulfur dissolves in the organic solvent and acts as a binder. Can be easily formed into a granular form, and can act as a binder even after removing the organic solvent, and granular insoluble sulfur having an appropriate particle breaking strength can be obtained.

The granular insoluble sulfur is highly fluid,
Further, when kneading with the rubber, it easily disintegrates and returns to a powder state, so that dispersibility in the rubber is good and stable physical properties of the rubber can be maintained.

[0016]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples. In these tests, the particle breaking strength is determined by pressing the sample placed on the electronic balance with a glass rod,
It was measured by the numerical value indicated by the electronic balance at the time when the sample was broken, and the remaining amount of adhesion was obtained by putting 100 g of the sample in a stainless steel round-bottomed cylindrical container (diameter 100 mm, height 60 mm). Name: SA-31 type, manufactured by Yamato Scientific Co., Ltd.], vibration width 30 mm, frequency 240 reciprocations /
After shaking for 10 minutes, the container was gently removed from the shaker, the sample was spontaneously discharged by tilting it at 180 degrees, and the amount of the sample remaining in the container was measured and determined.

The thermal stability is obtained by immersing a test tube containing 20 ml of mineral oil in an oil bath maintained at a temperature of 105 ° C.
When the temperature of the oil in the test tube reaches 105 ° C, 1.2 g of the sample is added to the test tube and heated for 15 minutes, then the test tube is taken out of the oil bath and rapidly cooled. Was thoroughly washed with, the soluble sulfur content was completely dissolved in carbon disulfide, filtered and dried, and the remaining insoluble sulfur content was weighed and calculated according to the formula 1.

[0018]

[Formula 1]

The dispersibility of insoluble sulfur in rubber is determined by winding 100 g of natural rubber around a roll of 45 to 55 ° C., adding a predetermined amount of insoluble sulfur and other compounding agents, cutting the product, and rolling it 6 times. This sheet was cut with a knife, and the state of the cut surface was visually checked to determine.

Regarding the blooming phenomenon, the rubber composition prepared for the dispersibility test was further passed through a roll heated to a temperature of 110 ° C. for 5 minutes and then allowed to stand at room temperature so that sulfur particles were not formed on its surface. It was judged by whether or not it was precipitated.

The physical properties of the vulcanized product were measured by press-vulcanizing a rubber composition containing insoluble sulfur at a temperature of 160 ° C. for 20 minutes, and then conducting a test according to JIS K6301.
The hardness was measured using an A-type tester of the same standard.

[0022]

Example 1 A high-speed mixer having a total volume of 70 liters of 10 kg of powdery insoluble sulfur (containing 0.2% of α-methylstyrene; the same applies hereinafter) having a pure content of 97% [trade name: Spartan Luther RM
O-50H type, manufactured by Fuji Paudal Co., Ltd.], while stirring the main shaft of the mixer at a rotation speed of 2000 to 2500 rpm, 6 liters of n-hexane was added and stirring and mixing were continued for 10 minutes. The obtained granules were placed in a hot air dryer set at a temperature of 70 ° C. and dried for 1 hour, and n-hexane was volatilized to form the whole amount of powdery insoluble sulfur into granules.

This product is a uniform particle having a particle size of about 0.5 mm, its breaking strength is 8 to 25 g, and the remaining amount of adhesion is 2.5 to 7.0.
g, thermal stability was 86.3%.

[0024]

Example 2 The same mixer used in Example 1 was used, and the pure content of 97
% Powdery insoluble sulfur (10 kg) is added to the rubber processing oil [trade name: # 310, manufactured by Nippon San Oil Co., Ltd.], which is composed of naphthene-based, aromatic-based and paraffin-based oil with stirring.
1.1 kg), 4.5 liters of n-hexane were added, and the mixture was stirred and mixed for 10 minutes, and the granules thus obtained were placed in a hot air dryer set at a temperature of 70 ° C and dried for 1 hour. , Granular insoluble sulfur containing rubber process oil was obtained.

This product is uniform particles containing 9.9% of rubber process oil and having a particle size of about 0.5 mm, and its breaking strength is 5 to 5.
25 g, residual adhesion amount was 3.0 to 8.0 g, and thermal stability was 86.6%.

[0026]

Example 3 The same mixer as used in Example 1 was used and the pure content of 97
% Powdery insoluble sulfur (10 kg) was added, 6 liters of isopropyl alcohol was added to this with stirring, and the mixture was stirred and mixed for 10 minutes. The granules thus obtained were dried with hot air at a temperature of 70 ° C. Put in the machine and dry for 1 hour,
The isopropyl alcohol was volatilized to form the whole amount of powdery insoluble sulfur into granules.

This product is a uniform particle having a particle size of about 0.5 mm, its breaking strength is 7 to 26 g, and the remaining amount of adhesion is 2.2 to 7.5.
g, thermal stability was 86.0%.

[0028]

Example 4 The same mixer used in Example 1 was used and the pure content of 97
% Of powdery insoluble sulfur was added thereto, 1.1 kg of the same rubber processing oil as used in Example 1 was added thereto with stirring, 4.5 liter of isopropyl alcohol was further added, and stirring and mixing were continued for 10 minutes. The obtained granules were put in a hot-air dryer set at 70 ° C. to volatilize isopropyl alcohol to obtain granular insoluble sulfur containing rubber process oil.

This product is uniform particles containing 9.9% of rubber process oil and having an average particle size of about 0.5 mm, and its breaking strength is 6 to
24 g, residual adhesion amount was 2.4 to 8.0 g, and thermal stability was 86.6%.

[0030]

Comparative Example 1 135 kg of 97% pure powdery insoluble sulfur and 15 kg of the same rubber process oil used in Example 2 were both charged into a Ledige mixer mixer having a capacity of 300 liters, and the main shaft was rotated at 115 rpm. After stirring and mixing for 10 minutes, no granular insoluble sulfur was obtained. The above-mentioned insoluble sulfur contains 10% of rubber process oil, the residual amount of adhesion is 60 ~ 90g, thermal stability
It was 86.5%.

[0031]

Example 5 100 parts by weight of natural rubber, 50 parts by weight of HAF carbon black, 5 parts by weight of zinc white, 2 parts by weight of stearic acid, 1 part by weight of phenyl-1-naphthylamine, 3 parts by weight of rubber process oil, N-oxydiethylene. 0.5 parts by weight of 2-benzothiazole sulfenamide and 6 parts by weight of the granular insoluble sulfur obtained in Example 1 were uniformly kneaded with a roll mixer to prepare a rubber composition. The results of evaluation tests conducted on the rubber composition are shown in Table 1.

[0032]

[Example 6] In Example 5, except that the granular insoluble sulfur was replaced by the one obtained by the method of Example 2, the same ingredients and the same amount were used, and these were uniformly kneaded by a roll mixer. A rubber composition was prepared by the above method, and its evaluation test was conducted.

[0033]

[Comparative Example 2] In Example 5, except that the same powdery insoluble sulfur as obtained in Comparative Example 1 (residual adhesion amount 60 to 90 g) was used, the same components and the same use amount were used, and these were used as rolls. When a rubber composition was prepared by uniformly kneading with a mixer and an evaluation test was conducted, the results were as shown in Table 1.

[0034]

[Comparative Example 3] In Example 5, rubber process oil was 10%.
Granular insoluble sulfur (powder strength of 100 g or more, residual adhesion amount of 1.0-) was obtained by pressure-molding the contained powdery insoluble sulfur under a pressure condition of 70-80 kg / cm ² using a roller compactor.
5.0), except that the same components and the same amount of use were used, and these were uniformly kneaded by a roll mixer to prepare a rubber composition, and the results of an evaluation test thereof are as shown in Table 1. Met.

[0035]

[Table 1]

[0036]

INDUSTRIAL APPLICABILITY Since the insoluble sulfur produced by the method of the present invention is a granular body and has an appropriate particle breaking strength, dust does not scatter when compounded in rubber, and moreover, vessel walls, etc. Since it does not adhere to, it is possible to significantly improve workability.

Further, the rubber composition of the present invention has extremely good dispersibility in rubber, does not cause blooming, and has physical properties of rubber because insoluble sulfur particles easily disintegrate into powder when kneading. It has the effect of greatly reducing variations.

Claims (4)

[Claims] 1. Granular insoluble sulfur with improved fluidity, characterized in that an organic solvent is added to insoluble sulfur powder to granulate, and the mixture is heated to a temperature of 120 ° C. or lower to volatilize the organic solvent. Manufacturing method. 2. A process for improving fluidity, which is characterized in that rubber process oil and an organic solvent are added to an insoluble sulfur powder to granulate, and the mixture is heated to a temperature of 120 ° C. or lower to volatilize the organic solvent. A method for producing granular insoluble sulfur. 3. Granular insoluble sulfur obtained by mixing an insoluble sulfur powder with an organic solvent and granulating and volatilizing the organic solvent to obtain 0.5 parts by weight of insoluble sulfur to 100 parts by weight of rubber. A rubber composition, which is compounded to be 10 parts by weight. 4. Granules composed of insoluble sulfur and rubber process oil, which are obtained by mixing an insoluble sulfur powder with an organic solvent and rubber process oil, granulating the mixture, and volatilizing the organic solvent, to 100 parts by weight of rubber. And a rubber composition containing 0.5 to 10 parts by weight of insoluble sulfur.